This invention is in the field of polyterpene resin compositions; more particularly, the invention relates to a composition comprising polyterpene resin and a blend of low molecular weight polyethylene based polymers.
Polyterpene resins are a class of thermoplastic resins or viscous liquids of amber color, obtained by polymerization of turpentine in the presence of catalysts such as aluminum chloride or mineral acids. Polyterpene resins are classified as natural for those made based on turpentine and synthetic for those made based on petroleum products. The resins are based on polymers of alpha- or beta-pinene. The resins are indicated to be useful in paints, wax polishes, rubber plasticizers, curing concrete, and impregnating paper.
Polyterpene resins have been blended with waxes and polymers to make hot melt adhesives as disclosed in the bulletin entitled, "ESCOREZ.RTM. 5000 Resins for Hot Melt Adhesives" published by Exxon Chemical Company. This bulletin discloses formulations which include wax, ethylene vinyl acetate copolymer, and resin. The ethylene vinyl acetate copolymer contemplated has a relatively high molecular weight as indicated by their melt indexes of 2.5 and 25. The waxes are indicated to be paraffin waxes. This bulletin also discloses that a series of blends had been prepared using ESCOREZ.RTM. 5300 with commonly used hot melting ingredients including low molecular weight polyethylene (Epolene C-10) produced by the Eastman Kodak Company. The bulletin disclosed blend ratios of 25/75, 50/50, and 75/25 of resins to modifier. The evaluation was directed to determine compatibility in both a molten state and in thin cast films. The low molecular weight polyethylene was found to be fully compatible in the resin blend. All of the resin blends showed good viscosity stability compared with the "neat" polyethylene, which gelled somewhat on extended aging. Films made of the high resin content blends were brittle.
Polyterpene resins are also known and advertised for use in tackifying compositions Typically, a minor amount of resin is used in such applications. Blends of resin into waxes have been disclosed for use as hot melt coatings. Typically, such blends include the wax as a major component and the resin as a minor component.
In summary, polyterpene resins are useful in adhesive applications such as pressure sensitive adhesives, hot melt adhesives and hot melt coating. Other uses include plastics modification, tackifying, additions to paints, varnishes and printing inks.
A use of particular interest is in hot melt coatings. Hot melt coating compositions are disclosed in the publication "Tech Book Facts, Wing Tack, Wing Tack 95 Tackifying Resin", by the Goodyear Chemical Company, which are useful in the packing industry. It discloses that the polyterpene resin has the distinct qualities of high gloss, heat sealibility, a minimum water vapor transmission rate, and viscosity stability. A typical recipe is indicated to be 20 parts of resins, 25 parts of ethylene vinyl acetate copolymer, and 55 parts of parafin wax.